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From:   "T.J. Mercier" <tjmercier@google.com>
Date:   Fri, 20 May 2022 09:25:38 -0700
Message-ID: <CABdmKX2Ok023rN1drQgXVZLKUO_DVYrzmEamCgMMu6BPO67yhQ@mail.gmail.com>
Subject: Re: [PATCH v7 0/6] Proposal for a GPU cgroup controller
To:     Tejun Heo <tj@kernel.org>
Cc:     Nicolas Dufresne <nicolas@ndufresne.ca>,
        Zefan Li <lizefan.x@bytedance.com>,
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On Fri, May 20, 2022 at 12:47 AM Tejun Heo <tj@kernel.org> wrote:
>
> Hello,
>
> On Tue, May 17, 2022 at 04:30:29PM -0700, T.J. Mercier wrote:
> > Thanks for your suggestion. This almost works. "dmabuf" as a key could
> > work, but I'd actually like to account for each heap. Since heaps can
> > be dynamically added, I can't accommodate every potential heap name by
> > hardcoding registrations in the misc controller.
>
> On its own, that's a pretty weak reason to be adding a separate gpu
> controller especially given that it doesn't really seem to be one with
> proper abstractions for gpu resources. We don't want to keep adding random
> keys to misc controller but can definitely add limited flexibility. What
> kind of keys do you need?
>
Well the dmabuf-from-heaps component of this is the initial use case.
I was envisioning we'd have additional keys as discussed here:
https://lore.kernel.org/lkml/20220328035951.1817417-1-tjmercier@google.com/T/#m82e5fe9d8674bb60160701e52dae4356fea2ddfa
So we'd end up with a well-defined core set of keys like "system", and
then drivers would be free to use their own keys for their own unique
purposes which could be complementary or orthogonal to the core set.
Yesterday I was talking with someone who is interested in limiting gpu
cores and bus IDs in addition to gpu memory. How to define core keys
is the part where it looks like there's trouble.

For my use case it would be sufficient to have current and maximum
values for an arbitrary number of keys - one per heap. So the only
part missing from the misc controller (for my use case) is the ability
to register a new key at runtime as heaps are added. Instead of
keeping track of resources with enum misc_res_type, requesting a
resource handle/ID from the misc controller at runtime is what I think
would be required instead.

> Thanks.
>
> --
> tejun